The association among negative symptoms, movement disorders, and frontal lobe psychological deficits in schizophrenic patients

Mechanisms of action of clozapine in the treatment of neuroleptic-resistant and neuroleptic-intolerant schizophrenia

The mechanisms of action which account for the effectiveness of clozapine as a pharmacotherapy for the treatment of neuroleptic non-responders and neuroleptic intolerant schizophrenic subjects remain elusive. We review recent data concerning the actions of clozapine in laboratory animals, and discuss the likely sites of action of clozapine and the receptors through which clozapine acts. We suggest that actions at dopamine D2 receptors in the caudate nucleus and putamen underlie the extrapyramidal side effects of conventional neuroleptics. In contrast, we propose that clozapine acts in the prefrontal cortex, specifically targeting an as yet unidentified DA receptor of the D2 family, to exert therapeutic actions in neuroleptic non-responders. We suggest that the ability of clozapine to augment extracellular dopamine levels in the prefrontal cortex may represent a key mechanism contributing to the therapeutic effects of this drug, and suggest some alternative approaches which might be expected to result in effects similar to those of clozapine.

Characterization of the deficit syndrome in drug-naive schizophrenia patients: the role of spontaneous movement disorders and neurological soft signs

This study aimed to characterize the deficit syndrome in drug-naive schizophrenia patients and to examine the relationship between deficit features and primary neurological abnormalities. Drug-naive schizophrenia patients (n = 102) were examined at baseline for demographics, premorbid functioning, duration of untreated illness (DUI), psychopathology, neurological signs, and deficit symptoms, and reassessed at 1-year follow-up. Neurological abnormalities were examined before inception of antipsychotic medication and included four domains of spontaneous movement disorders (SMD) and four domains of neurological soft signs (NSS). Patients fulfilling the deficit syndrome criteria at the two assessments (n = 20) were compared with nondeficit patients (n = 82) across demographic, clinical, and neurological variables. Deficit and nondeficit groups showed similar demographic characteristics and levels of psychotic, disorganization, and depressive symptoms. Compared with nondeficit patients, deficit patients showed poorer premorbid adjustment, higher premorbid deterioration, a lengthier DUI, and much poorer functional outcome. Relative to the nondeficit patients, those with the deficit syndrome showed higher levels of SMD--excepting akathisia--and NSS. This association pattern was also evident for deficit and neurological ratings in the whole sample of schizophrenia patients. Parkinsonism, motor sequencing, and release signs were all independently related to the deficit syndrome. These findings confirm that the deficit/nondeficit categorization is replicable and reliable in first-admission patients and raise the possibility that premorbid deterioration, deficit symptoms, and neurological abnormalities represent a triad of manifestations that share common underlying neurobiological mechanisms. More specifically, the data are consistent with a neurodevelopmental model of deficit symptoms involving basal ganglia dysfunction.

Willed action and its impairments

Actions are goal-directed behaviours that usually involve movem ent. There is evidence that intentional self-generated actions (willed actions) are controlled differently from routine, stereotyped actions that are externally triggered by environmental stimuli. We review evidence from investigations using positron emission tomography (PET), recordings of movement-related cortical potentials (MRCPs) or transcranial magnetic stimulation (TMS), and conclude that willed actions are controlled by a network of frontal cortical (dorsolateral prefrontal cortex, supplementary motor area, anterior cingulate) and subcortical (thalamus and basal ganglia) areas. We also consider evidence suggesting that some of the cognitive and motor deficits of patients with frontal lesions, Parkinson's disease, or schizophrenia as well as apathy and abulia and rarer phenomena such as primary obsessional slowness can be considered as reflecting im pairment of willed actions. We propose that the concept of a willed action system based on the frontostriatal circuits provides a useful framework for integrating the cognitive, motor, and motivational deficits found in these disorders. Problems remaining to be resolved include: identification of the component processes of willed actions; the specific and differential role played by each of the frontal cortical and subcortical areas in the control of willed actions; the specific mechanisms of impairm ent of willed actions in Parkinson's disease, schizophrenia, and frontal damage; and the precise role of the neurotransmitter dopamine in the willed action system.

White matter abnormalities in schizophrenia patients with tardive dyskinesia: a diffusion tensor image study

OBJECTIVE

Tardive dyskinesia (TD) is a severe side effect of antipsychotics. While increasing evidence suggests that damaged brain microcircuitry of white matter (WM) is responsible for the clinical symptoms in schizophrenia, no reports of WM abnormality associated with TD were noted.

METHOD

Brain white matter abnormalities were investigated among 20 schizophrenia patients with TD (Schizophrenia with TD group), 20 age-, gender-, and handedness-matched schizophrenic patients without TD (Schizophrenia without TD group), and 20 matched healthy subjects with magnetic resonance imaging and diffusion tensor imaging analysis. Voxel-wise analysis was used to compare fractional anisotropy (FA) maps of the white matter following intersubject registration to Talairach space. Clinical ratings included the Positive and Negative Symptoms Scale (PANSS), Abnormal Involuntary Movement Scale (AIMS), and the Simpson-Angus Scale (SAS).

RESULTS

The study subjects were 75% female with average of 40.1+/-9. 8 years. The Schizophrenia with TD group had significantly higher PANSS total scores (p=0.024), PANSS negative score (p=0.001), SAS (p<0.001) and AIMS (p<0.001) scores; and demonstrated more widespread FA decreases than the Schizophrenia without TD group, especially over the inferior frontal gyrus, temporal sublobar extranuclear WM (around the basal ganglion), parietal precuneus gyrus WM (around somatosensory cortex), and medial frontal gyrus WM (around dorsolateral prefrontal cortex). The AIMS (p<0.01) and SAS (p<0.01) score positively correlated with decreased FA over these areas, and PANSS negative score positively correlated with FA decrease over medial frontal gyrus WM (p<0.01).

CONCLUSIONS

More widespread abnormality of white matter was noted among schizophrenia patients than those without, especially involved cortico-basal ganglion circuits with clinical symptom correlation of involuntary movements and negative symptoms. Further studies with larger sample size are required to validate the findings.

Is executive impairment associated with schizophrenic syndromes? A meta-analysis

BACKGROUND

A key neuropsychological proposal in schizophrenia is that negative and disorganization symptoms are associated with different patterns of impairment on executive tasks.

METHOD

Studies reporting correlations between positive, negative or disorganization symptoms and any type of executive test were meta-analysed. The influence of moderating factors was also examined, including age, treatment and stage of illness and whether symptoms were relapsing or persistent. The magnitudes of the correlations were compared with those for general intellectual impairment.

RESULTS

Pooled correlations between executive impairment and both negative symptoms and disorganization were significant in the small-to-moderate range. That for positive symptoms ('reality distortion'), however, was close to zero. The pattern of correlations among different executive tests differed significantly for negative symptoms and disorganization. Patients with stable clinical pictures showed significantly higher correlations with executive impairment than those with relapsing and remitting illnesses. Both negative symptoms and disorganization also correlated significantly with general intellectual function as indexed by current IQ.

CONCLUSIONS

Meta-analysis supports the view that negative symptoms and disorganization are associated with partially dissociable patterns of executive impairment. However, co-existent general intellectual impairment has been an important confounding factor in the studies to date.

Relations between movement disorders and psychopathology under predominantly atypical antipsychotic treatment in adolescent patients with schizophrenia

OBJECTIVE

To examine relations between movement disorders (MD) and psychopathological symptoms in an adolescent population with schizophrenia under treatment with predominantly atypical antipsychotics.

METHOD

MD symptoms and psychopathology were cross-sectionally assessed in 93 patients (aged 19.6 +/- 2.2 years) using Tardive Dyskinesia Rating Scale (TDRS), Abnormal Involuntary Movement Scale (AIMS), Extrapyramidal Symptom Scale (EPS), Barnes Akathisia Scale (BAS), Brief Psychiatric Rating Scale (BPRS) and the Schedule for Assessment of Negative/Positive Symptoms (SANS/SAPS).

RESULTS

All patients with MD symptoms (n = 37; 39.8 %) showed pronounced global psychpathological signs (SANS/SAPS, BPRS: p = 0.026, p = 0.033, p = 0.001) with predominant anergia symptoms (p = 0.005) and inclinations toward higher anxiety- and depression-related symptoms (p = 0.051) as well as increased thought disturbance (p = 0.066). Both negative symptoms and anergia showed trends for positive correlations with tardive dyskinesia (p = 0.068; p = 0.065) as well as significant correlations with parkinsonism symptoms (p = 0.036; p = 0.023). Akathisia symptoms correlated significantly with hostile and suspicious symptoms (p = 0.013). A superfactor-analysis revealed four factors supporting the aforementioned results.

CONCLUSION

MD symptoms and psychopathology are in some respects related to each other. Motor symptoms representing on the one hand trait characteristics of schizophrenia might additionally be triggered by antipsychotics and finally co-occur with more residual symptoms within a long-term treatment.

Predictors of neuroleptic-induced dyskinesia and parkinsonism: the influence of measurement methods and definitions

The accurate and objective measurement of abnormal, involuntary movements remains highly desirable, whether the movements are secondary to pharmacotherapy or an expression of the primary illness. In a previous study, we found that the prevalence of tardive dyskinesia in a sample of 100 subjects ranged from 28% when using the Abnormal Involuntary Movement Scale (AIMS) or the Dyskinesia Identification Scale, Condensed User Version (DISCUS) to 62% using an instrumental measurement (IM) of peripheral dyskinesia. The goal of this study was to examine the relationship between various risk factors for tardive dyskinesia as predictor variables, and the AIMS, DISCUS, and IMs of dyskinesia, tremor, and velocity of motor movement as dependent variables. The sample consisted of 100, mostly patients with schizophrenia. Poor performance on the Mini-Mental State Examination (MMSE) and increasing age were the most consistent predictors of dyskinetic and parkinsonian movements. Various predictors were associated with specific abnormal movements. Head injury was related to slower speed of motor movements and the total DISCUS score. A history of smoking was associated with less IM dyskinesia. For those with coexisting parkinsonism and dyskinesia, significant associations were found with head injury, diabetes mellitus, and an AIMS score of 2 or greater in 2 body areas. Various classes of psychotropic agents seemed to have little influence on the MMSE or the development of dyskinesia and parkinsonism. Increasing age and a lower score on the MMSE seem to be particularly helpful in gauging the risk for parkinsonian and dyskinetic movements.

Unawareness in schizophrenia: neuropsychological and neuroanatomical findings

The lack of insight in schizophrenia has so far been interpreted as a primary symptom of the illness, namely a defensive mechanism rather than a neurologically-based condition. However, recent findings have emphasized its relationship with damage to specific brain areas as well as the domain specificity in which it may occur. This supports a neuropsychological interpretation of the lack of insight in schizophrenia. The present article reviews the foregoing data, and takes into account the most relevant anatomo-clinical results. There is evidence that the lack of insight in schizophrenia may occur as a neurological disease per se following brain damage that seems related to frontal lobe areas. Additionally, it could either be related to all aspects of the disease or be domain-specific, occurring for one kind of symptom but not for others. These data indicate several analogies with the phenomenon called anosognosia for a neurological deficit.

Induction of differential patterns of local cerebral glucose metabolism and immediate-early genes by acute clozapine and haloperidol

Atypical antipsychotic drugs, such as clozapine, show many differences in their actions as compared to typical antipsychotic drugs, such as haloperidol. In particular, the neuroanatomical substrates responsible for the superior therapeutic profile of clozapine are unknown. In order to identify regions of the CNS which are affected either differentially or in parallel by clozapine and haloperidol, we have used 2-deoxyglucose autoradiography to monitor local cerebral glucose utilisation (LCGU), in parallel with in situ hybridisation to monitor the expression of five immediate-early genes (c-fos, fos B, fra 1, fra 2 and zif 268). Clozapine (20 mg/kg i.p.) caused a reduction in LCGU in many areas of the psychosis-related corticolimbothalamic and Papez circuits, such as the anterior cingulate and retrosplenial cortices and the mammillary body. Haloperidol (1 mg/kg i.p.) showed less ability to modulate LCGU in these regions. Clozapine also increased immediate-early gene expression in these limbic circuits, although the pattern of induction was different for each gene, and also differed from the pattern of effects on LCGU. The only region which displayed similar effects with both antipsychotics was the anteroventral thalamus, with LCGU and c-fos mRNA expression being altered similarly by both drugs. This further supports the hypothesis of the thalamus being a common site of antipsychotic action. Since the Papez circuit has been implicated in emotive learning, and to be involved in mediating the negative symptoms associated with schizophrenia, the greater action of clozapine on regions within this circuit may also provide clues to the atypical antipsychotic's superior efficacy against negative symptoms. This is one of the first studies which provides a direct comparison of regional activity as assessed by LCGU and by a panel of IEGs. The results emphasise the necessity of monitoring a number of different parameters of regional activity in order to identity the neuroanatomical substrate for actions of a drug in the CNS.

Effects of the adenosine A(1) receptor agonist N(6)-cyclopentyladenosine on phencyclidine-induced behavior and expression of the immediate-early genes in the discrete brain regions of rats

Because of the possible interaction between adenosine receptors and dopaminergic functions, the compound acting on the specific adenosine receptor subtype may be a candidate for novel antipsychotic drugs. To elucidate the antipsychotic potential of the selective adenosine A(1) receptor agonist N(6)-cyclopentyladenosine (CPA), we examined herein the effects of CPA on phencyclidine (PCP)-induced behavior and expression of the immediate-early genes (IEGs), arc, c-fos and jun B, in the discrete brain regions of rats. PCP (7.5 mg/kg, s.c.) increased locomotor activity and head weaving in rats and this effect was significantly attenuated by pretreatment with CPA (0.5 mg/kg, s.c.). PCP increased the mRNA levels of c-fos and jun B in the medial prefrontal cortex, nucleus accumbens and posterior cingulate cortex, while leaving the striatum and hippocampus unaffected. CPA pretreatment significantly attenuated the PCP-induced increase in c-fos mRNA levels in the medial prefrontal cortex and nucleus accumbens. CPA also significantly attenuated the PCP-induced arc expression in the medial prefrontal cortex and posterior cingulate cortex. When administered alone, CPA decreased the mRNA levels of all IEGs examined in the nucleus accumbens, but not in other brain regions. Based on the ability of CPA to inhibit PCP-induced hyperlocomotion and its interaction with neural systems in the medial prefrontal cortex, posterior cingulate cortex and nucleus accumbens, the present results provide further evidence for a significant antipsychotic effect of the adenosine A(1) receptor agonist.

Insight in schizophrenia: its relationship to measures of executive functions

Lack of awareness of specific symptoms among persons with schizophrenia has not been adequately studied in the context of neuropsychological function. The purpose of this study is to investigate whether poor insight as measured by the Scale to Assess Unawareness of Mental Disorder is empirically related to performance measures having a known association with executive functions in a group of individuals with chronic schizophrenia. The results showed that unawareness and misattribution of negative symptoms are significantly associated with deficits in some aspects of executive functioning even after a test of general intelligence had been partialed from the analyses. We conclude that unawareness of negative symptoms is associated with executive functioning in individuals with chronic schizophrenia. Unawareness of other symptoms (i.e., positive symptoms) may reflect dysfunction in other types of neuropsychological processes, or it may reflect motivation to deceive oneself or others.

Modification of haloperidol-induced pattern of c-fos expression by serotonin agonists

Acute challenge with clozapine and haloperidol produce different anatomical patterns of c-fos expression in the forebrain. The pharmacological profile of atypical antipsychotics suggests that serotonin might contribute to the unique therapeutic benefits of these drugs. In order to test this possibility, we examined the abilities of 5-HT1A and 5-HT2A/2c agonists to modify the pattern of c-fos expression induced by haloperidol and clozapine. Various groups of rats were pretreated with either saline, DOI, 8-OH-DPAT, and 8-OH-DPAT + DOI 30 min prior to haloperidol or clozapine administration. Rats were killed 90 min after antipsychotic administration. In saline-pretreated rats, haloperidol produced intense Fos-LI in all four striatal quadrants while the effect of clozapine was restricted to the medial part of the striatum. Prior administration of 8-OH-DPAT significantly reduced haloperidol-induced Fos-LI in all four striatal quadrants while DOI and 8-OHDPAT + DOI significantly reduced Fos-LI only in dorso- and ventrolateral quadrants. In the nucleus accumbens, haloperidol induced intense Fos-LI in the core and the shell regions whereas clozapine induced c-fos expression only in the shell. Pretreatment with 8-OHDPAT in haloperidol treated rats reduced Fos-LI in the core region yielding to a c-fos pattern similar to that induced by clozapine. In the prefrontal cortex of saline-pretreated rats, haloperidol produced a moderate c-fos expression compared with the intense expression produced by clozapine. Pretreatment with serotonin agonists before haloperidol brought the number of FOS-positive neurons to the same level as in clozapine treated rats. These results show the ability of 5-HT agonists to transform the typical pattern of c-fos expression induced by haloperidol into a pattern resembling that of clozapine.

A multimethod approach to assessing perseverations in schizophrenia patients

Perseverations have been associated with frontal lobe impairment and are often observed among schizophrenia patients. We assessed perseverations in schizophrenia patients (N = 71) using the Wisconsin Card Sorting Test (WCST) and a new Rorschach perseveration scale which yields three perseveration scores. We also compared the results of the schizophrenia patients with those of a normal comparison group (N = 71). We found that schizophrenia patients demonstrated a high number of perseverations on both the WCST and the Rorschach perseveration scale when compared to the normal comparison subjects. Among schizophrenia patients, WCST perseverative responses were significantly correlated with Rorschach-derived stuck-in-set perseverations, WAIS-R Vocabulary scores and negative symptom ratings. No significant differences in any of the measures of perseveration were found to be associated with diagnostic subtype. Finally, WCST and Rorschach measures for the schizophrenia and normal comparison participants were entered into a logistic regression. The WCST total errors and the three Rorschach perseveration measures resulted in the correct classification of 89.4% of the total cases, with a sensitivity of 91%, specificity of 91% and positive predictive power of 87.8%. These data provide evidence that perseverative behavior is widely observed in schizophrenia patients using a variety of instruments. The authors discuss the benefit of using multiple measures of perseveration in schizophrenia research.

Glutamate in schizophrenia: clinical and research implications

The excitatory amino acids, glutamate and aspartate, are of interest to schizophrenia research because of their roles in neurodevelopment, neurotoxicity and neurotransmission. Recent evidence suggests that densities of glutamatergic receptors and the ratios of subunits composing these receptors may be altered in schizophrenia, although it is unclear whether these changes are primary or compensatory. Agents acting at the phencyclidine binding site of the NMDA receptor produce symptoms of schizophrenia in normal subjects, and precipitate relapse in patients with schizophrenia. The improvement of negative symptoms with agents acting at the glycine modulatory site of the NMDA receptor, as well as preliminary evidence that clozapine may differ from conventional neuroleptic agents in its effects on glutamatergic systems, suggest that clinical implications may follow from this model. While geriatric patients may be at increased risk for glutamate-mediated neurotoxicity, very little is known about the specific relevance of this model to geriatric patients with schizophrenia.

Construct validity of negative symptoms: an empirical and conceptual review

The construct validity of negative symptoms is reviewed, and findings on deficit negative symptoms are also incorporated. A valid negative symptom construct should: (a) have replicable relationships with observable phenomena and other constructs; (b) have good reliability, temporal stability, and homogeneity; and (c) predict prognosis and response to treatment, possess convergent and discriminant validity, and be useful to clinicians. Although a number of well-replicated findings provide support for the validity of the construct, modification is warranted. Specifically, the data suggest that there is a highly correlated set of negative symptoms, which includes flat affect, alogia, anhedonia, and avolition. Primary and enduring symptoms from this set have good predictive and discriminant validity and can be studied in the context of the deficit syndrome, as well as with current negative symptom rating scales. Future studies should examine whether deficit negative symptoms are better conceptualized as a dimension or a category, elucidate the relationship between deficit symptoms and additional clinical and behavioral variables (e.g., response to newer neuroleptic medications and diminished emotional responding), and explore differences between the pattern of correlates of deficit symptoms and those of the positive and thought disorder symptoms.

Caudate nucleus morphology in tardive dyskinesia

OBJECTIVE

The objective of this project was to test whether there are differences in the size of the caudate nucleus in schizophrenic in-patients with and without tardive dyskinesia.

METHOD

The study was cross-sectional in design, examining group differences between institutionalised schizophrenic patients with and without tardive dyskinesia, using non-enhanced computerised tomography scans of the brain. The group comprised 15 schizophrenic patients with persistent tardive dyskinesia and 21 in-patient schizophrenic controls who were group-matched for demographic variables.

RESULTS

The dyskinetic subjects had a significantly larger left caudate nucleus and tended to have a larger right caudate nucleus than the controls. There were no differences between the groups on any of the measures of cerebral atrophy.

CONCLUSIONS

The findings can be understood within the context of models of neostriatal function. It is possible that a larger caudate nucleus could be used to identify patients at risk of developing tardive dyskinesia.

Essential fatty acids and abnormal involuntary movements in the general male population: a study of men born in 1933

Spontaneous and tardive dyskinesias were studied in a random population sample of 446 men, aged 59 years. Dyskinesia, defined as an AIMS score of at least 2 in any body part, was seen in 15.1% (n = 74). Dyskinetic men had a higher cigarette consumption, and they had higher frequencies of psychiatric morbidity and exposure to neuroleptics. Dyskinesia was also associated with several abnormalities in EFA concentrations in plasma, but the most consistent finding was the low arachidonic acid levels in phospholipids, triglycerides and cholesterol esters. In a logistic regression model, cigarette consumption (P < 0.02), exposure to neuroleptics (P < 0.01), and low arachidonic acid levels in the phospholipid fraction (P < 0.0001) were independently associated with dyskinesia.

Tardive dyskinesia and positive and negative symptoms of schizophrenia. A study using instrumental measures

BACKGROUND

Controversy surrounds the relationship between tardive dyskinesia (TD) and symptoms of schizophrenia. While some studies reported that negative symptoms of schizophrenia may be a risk factor for TD, others reported a relationship between TD and positive symptoms.

METHOD

Eighty-four patients were studied, of whom 47 met criteria for TD. Clinical and instrumental procedures were used to increase the sensitivity of our assessments of the presence and severity of TD. Stepwise logistic and linear regression procedures were used to identify demographic variables, psychopathology, and motor parameters associated with the presence and severity of TD.

RESULTS

A 3-factor model consisting of age, clinical tremor, and negative symptoms explained 25% of the variance in clinical TD severity. A 6-factor model consisting of female gender, instrumental and clinical measures of parkinsonism, positive, and negative symptoms explained 49% of the variance in severity of instrumentally derived dyskinesia.

CONCLUSIONS

These results suggest that the presence of TD may be associated with positive symptoms; that the severity of TD may be related to negative symptoms; and that the relationship between negative symptoms and TD severity may be influenced by the presence of parkinsonism.

Risk factors for orofacial and limbtruncal tardive dyskinesia in older patients: a prospective longitudinal study

Although there is a consensus that orofacial and limbtruncal subtypes of tardive dyskinesia (TD) exist and may represent distinct pathophysiologic entities, few studies have examined the incidence of and risk factors associated with the development of these TD subtypes. Two hundred and sixty-six middle-aged and elderly outpatients with a median duration of 21 days of total lifetime neuroleptic exposure at study entry were evaluated at 1- to 3-month intervals. Using "mild" dyskinesia in any part of the body for diagnosis of TD, the cumulative incidence of orofacial TD was 38.5 and 65.7% after 1 and 2 years, respectively, whereas that of limbtruncal TD was 18.6 and 32.6% after 1 and 2 years. Preclinical dyskinesia was predictive of both orofacial and limbtruncal TD. History of alcohol abuse or dependence was a significant predictor of orofacial TD only whereas tremor was a significant predictor of limbtruncal TD only. Findings support suggestions that orofacial and limbtruncal TD may represent specific subsyndromes with different risk factors.

Movements in never-medicated schizophrenics: a preliminary study

Descriptions of schizophrenia dating to the beginning of this century include mention of abnormal movements which are similar to tardive dyskinesia (TD), currently thought to be sequelae of neuroleptic medication. In order to examine the extent to which such movements might appear in the normal course of schizophrenia, we examined a sample of 22 never-medicated DSM-III-R schizophrenics who presented for treatment at a psychiatric center in Casablanca, Morocco. Duration of illness in this sample ranged from 1 to 10 years. Patients were assessed for choreoathetoid movements using the Abnormal Involuntary Movement Scale (AIMS). Videotaped and live examinations were rated by the investigators. Three patients (14%) met research diagnostic criteria for probable SD. Mild movements in one body part (AIMS = 2) were seen in an additional five (23%) patients. The movements were characteristic of TD, although their somatic distribution differed from previous studies. Total AIMS score increased with age and duration of illness (r = 0.64, P < 0.01). These findings suggest that choreoathetoid movements may appear spontaneously in patients with schizophrenia.

The effects of antipsychotic drugs on Fos protein expression in the prefrontal cortex: cellular localization and pharmacological characterization

The assessment of immediate-early gene induction has proven to be a useful method for delineating the neural systems that subserve antipsychotic drug actions. In order to differentiate the sites and mechanisms of action of typical and atypical antipsychotic drugs, we examined the effects of antipsychotic drugs on Fos protein expression in the medial prefrontal cortex. The atypical antipsychotic drug clozapine selectively increased the number of neurons that expressed Fos-like immunoreactivity in the prefrontal cortex, targeting the deep layers of the infralimbic and prelimbic cortices. Pyramidal cells were the major cell type in which Fos was expressed. A small number of calbindin-like immunoreactive, but not parvalbumin- or reduced nicotinamide adenine dinucleotide phosphate diaphorase-containing, interneurons also expressed Fos after clozapine challenge. Immunoblot studies revealed that clozapine induced Fos protein in the infralimbic and prelimbic cortices. Other antipsychotic drugs that are D2 receptor antagonists, including haloperidol, raclopride, sulpiride, remoxipride and loxapine, did not alter Fos expression. The clozapine-induced increase in Fos expression was also not attributable to actions at the D1 dopamine receptor, nor to serotonin type 2a/2c receptor antagonism or combined serotonin type 2-D2 dopamine receptor antagonism. The ability of clozapine to block alpha 1-adrenergic or muscarinic cholinergic receptors did not contribute to the unique actions of clozapine. Despite the inability of dopamine receptor antagonists other than clozapine to elicit an increase in Fos expression, both the mixed D1-D2 dopamine agonist apomorphine and the D2-like agonist quinpirole increased Fos protein levels in the prefrontal cortex. However, neither pretreatment with sulpiride to block D2/3/4 dopamine receptors or SCH 23390 to block D1/5 dopamine receptors modified the Fos response to clozapine. Since dopamine receptor antagonist pretreatments did not attenuate the clozapine-elicited Fos expression, but D2 agonists increased cortical Fos expression, clozapine may act in the prefrontal cortex on an as yet undefined dopamine receptor. In contrast to the nucleus accumbens shell, where all antipsychotic drugs increase Fos expression, only clozapine induced Fos in the medial prefrontal cortex. These observations suggest that the ability of clozapine to treat schizophrenic patients who are resistant to the therapeutic benefits of conventional antipsychotic drugs may occur through actions in the prefrontal cortex.

Neuropsychological deficit in newly diagnosed patients with schizophrenia or schizophreniform disorder

Forty-six patients with schizophrenia or schizophreniform disorder admitted to hospital for the first time were compared with 21 healthy volunteers on neuropsychological tests reflecting prefrontal and left respectively right hemisphere function. The patients with schizophrenia or schizophreniform disorder had a poorer performance on neuropsychological tests (such as Wisconsin Card Sorting) compared with healthy volunteers. Both left and right hemisphere seemed to be involved. Especially poor performance was found on somewhat complicated tests requiring ability of analysis, abstraction and memory, thus indicating dysfunction of prefrontal and temporohippocampal regions. Signs of sulcal enlargement and size of lateral ventricles on computed tomographic scan correlated with poor test performance on some tests both in patients and in healthy volunteers. No correlations were found between performance on neuropsychological test and negative symptoms.